Vacuum chambers are used in many useful industrial production environments, including vacuum casting and metallurgy, aerospace and satellite testing, automotive parts manufacturing, semiconductor and flat panel display manufacturing, research and medical processes. In these applications the work pieces involved are typically sensitive to contaminating matter and must be protected. A gate valve is often paired with a vacuum chamber to provide a means of entry and exit of the work piece from the chamber or to isolate the chamber from a vacuum source such as a vacuum pump. Gate valves are chosen in these applications because they present fewer moving parts than other types of valves. The reduction of moving parts reduces the possibility of work piece contamination from metal particulates shed from frictional engagement between parts.
Pendulum gate valves are especially desirable for vacuum chamber applications due to their compact configuration, high cycle rates, low maintenance and low level of metal particulate generation. U.S. Pat. No. 6,474,622 issued to Ito discloses a typical pendulum gate valve for use with a vacuum chamber having a multitude of roller pins which engage within an identical plurality of cam orifices imparted into a stationary bar member. A movable member containing the roller pins slides back and forth in relation to the bar member to actuate the mating of a valve plate with a housing of the pendulum gate valve. The added aspect of a plurality of rollers riding back and forth in a plurality of cam orifices lends to a higher probability of metal particulate contamination due to the frictional engagement of this many components. Furthermore, this pendulum gate valve only seals against the valve housing when the valve seat face of the valve plate is in contact with the vacuum environment inside of a vacuum chamber. The vacuum naturally suctions the valve seat face against the valve housing. This type of sealing is termed “easy way” sealing. The opposite sealing method has the valve seat face in contact with the atmosphere, such that the valve seat face is being drawn away from the valve housing by the difference in pressure between the vacuum side and atmosphere side. This type of sealing is termed “hard way” sealing.
Ideally, a gate valve mechanism would have the qualities of: 1) creating minimal particulate contamination; and 2) have the quality of being able to remain in a sealing condition whether the valve seat face is oriented as an easy way seal or a hard way seal. The present invention incorporates these two qualities.
The foregoing reflects the state of the art of which the inventor is aware, and is tendered with a view toward discharging the inventor's acknowledged duty of candor, which may be pertinent to the patentability of the present invention. It is respectfully stipulated, however, that the foregoing discussion does not teach or render obvious, singly or when considered in combination, the inventor's claimed invention.